I remember this question has come up several times in the past. The answer is no unfortunately.
I have used YouMail in the past to handle voicemails. They email you or you can open the voicemails in their app. Delete without listening from the app or email is a lot easier and you avoid the persistent voicemail notificaiton on your phone.
You can also achieve this by enabling conditional call forwarding to your Fongo number.
I'm trying this right now. So I'm using a greeting of straight nothing for as long as I was allowed (around 90 seconds) but I'm curious how this will prevent them from leaving messages. Since they're all bots, won't they just wait out my greeting and then leave a voicemail regardless? Thanks for helping
I will be sure to try your method next.
Thanks for replying
On some phones, you can install an app that will automatically answer the call and then just hang up on the person. For example, in Android one such program is called No Spam No Voicemail. The app itself is a little buggy (default settings don't work for me), but after tinkering with the settings, this app will answer a calls from specified phone numbers after one ring and then hang up on them. If that app isn't to your liking, there are others available as well.